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Add this to your list of nightmare jobs: prehistoric dentist. Had the profession existed 1.8 million years ago, it would have encountered an ancient human relative with a disconcertingly common dental disorder: weakened, pockmarked teeth resembling the surface of a golf ball.

The patient in question is Paranthropus robustus, a massive-jawed, thick-molared creature that looked a bit like a gorilla and feasted on tropical grasses, hard seeds and nuts, and fibrous fruits in southern Africa. Scientists have long suspected P. robustus’s tough, gritty diet contributed to the overall poor condition of the species’s fossil teeth found over the years.

Hoping to learn more, paleontologists compared hundreds of fossilized P. robustus teeth, pictured above, with those of other southern African hominins such as Australopithecus sediba and A. africanus that lived at roughly the same time, as well as with more recent hominins and living apes. The golf ball–like pitting was a common feature of P. robustus teeth, showing up in 47% of baby teeth and 14% of permanent teeth of the species, whereas it occurred only in about 7% and 4%, respectively, of the baby and permanent teeth of the other ancient hominins combined. These pits in the teeth enamel would have made them wear down quickly and break easily.

How did P. robustus develop this condition? In modern humans, the genes responsible also contribute to thick, dense enamel. It’s possible, the researchers suggest, that the defect was a side effect of evolving thicker, denser teeth to cope with the species’s rough diet.